According to my "ROYAL NAVY AND ROYAL MARINES; A guide to careers in the Royal Navy" bookley from the AFCO:
Medical and eye test
Specialist brancg interviews/auditions/test (if required)
Security and reference checks
Admiralty interview board (AIB).[ This is the navy's officer selection board. ]
Start initial training.
Before anyone tells me I'm wrong, I got this from the guide. I'm not sure, but I think the PJFT is around the same time as the medical isn't it?